NUMERICAL SIMULATION OF SEGREGATION PHENOMENA COUPLED WITH PHASE CHANGE AND FLUID FLOW: APPLICATION TO METAL MATRIX COMPOSITES PROCESSING

摘要

The injection of a liquid metal through a fibrous preform, located in an initially preheated mold, is one of the techniques used to manufacture metal matrix composites (MMCs). In order to reduce the chemical reactions between the fibers and the metal matrix, the fibrous reinforcement and the mold are commonly preheated up to initial temperatures much lower than the metal solidification temperature. Therefore, local metal solidification instan_taneously occurs on fiber during liquid metal infiltration. When infiltrating metal alloy, unlike what happens when infiltrating a pure metal, both temperature and composition may vary within the matrix; this heterogeneity induces segregation within composites. A fiber scale numerical simulation was developed taking into account coupled physical phenomena which occur during the processing: flow of the liquid metal around the fibers, phase change phenomena, solute redistribution at the liquidlsolid interface during alloy solidification, and species diffusion. This model predicts the segregation phenomena associated with fibrous preform infiltration by a binary alloy.